Elastic tie down

ABSTRACT

A tie down for connecting two objects. The tie down has an elastic tube having an unstretched state and a stretched state, a braided line extending through the tube, with the line having a compressed state and an uncompressed state, and a securement at each tube end to secure the line to the tube such that the line is in its compressed state when the tube is in its unstretched state and the line is in its uncompressed state when the tube is in its stretched state. Each end has an attachment for attaching to the objects.

CROSS-REFERENCES TO RELATED APPLICATIONS

Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

REFERENCE TO A SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTINGCOMPACT DISK APPENDIX

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to tethers, more particularly, toexpandable tethers for securing boats and the like.

2. Description of the Related Art

The elastic tie down is a well-known device developed to restrain anobject from moving away from a another object, for example, a boat froma dock. Elastic tie downs permit some relative movement between therestrained objects so that small relative motions can be accommodatedwithout creating large stresses and damage to the restrained objects.

To prevent overstressing the tie down to the breaking point, it is knownto combine a limiting component with an elastic component. The elasticcomponent provides resilient restraint against separation, and thelimiting component remains slack. When the separating force reaches apredetermined value, the elastic component becomes stretched such thatthe limiting component is taut and prevents further stretching of theelastic component. Examples of such tie downs are disclosed in U.S. Pat.Nos. 1,296,057, 2,991,524, and 4,694,541. The main shortcoming of thesetie downs is their bulk. The elastic component is an elastic tubethrough which the limiting component, such as an inelastic rope,extends. When there is no separating force on the tie-down, the rope isbundled haphazardly within the tube, meaning that the tube must beseveral times the thickness of the rope, depending upon the amount ofstretch permitted.

In an alternate construction, the elastic component forms a core to abraided line, the limiting component. When the elastic component is notstretched, the braided line is compressed. Since the line is notbundled, the tie down is thinner than the tie downs with the internallimiting component. However, since the braid on the line is across-hatch of threads, it is not smooth and easy to snag, particularlyin the unstretched condition.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide an elastic tie downthat is less bulky and less prone to snag than those of the prior art.

The present invention is a tie down for connecting two objects. It hasan elastic tube having an unstretched state and a stretched state, abraided line extending through the tube, with the line having acompressed state and an uncompressed state, and a securement at eachtube ends to secure the line to the tube such that the line is in itscompressed state when the tube is in its unstretched state and the lineis in its uncompressed state when the tube is in its stretched state.There is an attachment at each end for attaching to the objects.

In one configuration of the tie down, the inside diameter of theunstretched tube is at least as large as the compressed diameter of theline so that the line can fully compress within the tube without causingradially stretching of the tube. In another configuration, the insidediameter of the unstretched tube is at least as large as theuncompressed diameter of the line so that the fully compressed linecauses the tube to stretch radially.

The securement can come in a number of different forms and must bestrong enough to prevent separation of the tube from the line while atfull extension. The present invention contemplates the use of adhesives,mechanical clamps, and heat shrink tubing. Mechanical clamps can beeither permanent or temporary.

Optionally, a lubricant is used in the tube to reduce wear as a resultof the friction between the line and tube as the tie down is stretchedand relaxed.

Other objects of the present invention will become apparent in light ofthe following drawings and detailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and object of the presentinvention, reference is made to the accompanying drawings, wherein:

FIG. 1 is a perspective view in phantom of the tie down of the presentinvention;

FIG. 2 is a side, cutaway view of the tie down of FIG. 1 in itsquiescent state;

FIG. 3 is a side, cutaway view of the tie down of FIG. 1 in itsstretched state;

FIG. 4 is an enlarged view of a braided line;

FIG. 5 is an enlarged, cross-sectional view of an adhesive and shrinktubing securement;

FIG. 6 is an enlarged, cross-sectional view of a crimp securement; and

FIG. 7 is an enlarged, cross-sectional view of an alternateconfiguration of a tie down attachment.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is an elastic tie down that combines a narrowcross-section with a smooth exterior. The tie down 10, shown in FIG. 1,has a braided line 12 extending through an elastic tube 14. The line 12is secured to the tube 14 at the ends 20 of the tube 14, as at 16. Theends of the tie down 10 has attachments 18 for attaching the tie down tothe item to be secured. In its quiescent state, the tube 14 isunstretched and the line 12 is compressed within the tube 14, as in FIG.2. In its stretched state, the tube 14 is stretched until the line 12 istaut, as in FIG. 3.

The line 12 for use by the present invention is braided. Braided line ismade by interweaving three or more separate strands 22 of one or morematerials in a diagonally overlapping pattern, as shown in FIG. 4.Simple braids with more than three strands 22 can be flat or tubular andgenerally contain an odd number of strands.

One characteristic of a braided line 12 that is desirable for thepresent invention is that it stretches and compresses as a result oflongitudinal force. As the line 12 is pulled apart, the braid strands 22become more parallel to each other. At the maximum usable stretch, thatis, the maximum amount of stretch that can be employed for a particularapplication, the line 12 is uncompressed and has an uncompresseddiameter. As the line 12 is pushed together longitudinally, the braidstrands 22 become more perpendicular to each other. At the maximumusable compression, that is, the minimum length of the line 12 that canbe employed for a particular application, the line 12 is compressed andhas a compressed diameter.

The material of which the line 12 is constructed is determined by theamount of tension force the tie down 10 is expected to endure and thedesired working life of the tie down 10, both of which are determined byapplication for which the tie down 10 is designed. Possible materialsinclude nylons, polyesters, polypropylenes, aramids, and the like. Eachmaterial has its characteristic advantages and disadvantages forparticular applications including, for example, strength, resistance toabrasion, and cost. The materials may be used singly or in combination,as appropriate.

The elastic tube 14 is a hollow cylinder of elastic material. With mostmaterials, the tube 14 can stretch both longitudinally along its lengthand radially in its diameter. The material of which the tube 14 isconstructed is determined by the amount of force the tie down 10 isexpected to endure and the desired working life of the tie down 10, bothof which are determined by application for which the tie down 10 isdesigned. Possible materials include silicones, urethanes, gum rubbers,latexes, neoprenes, polystyrenes, polypropylenes, polyethylenes,fluoroelastomers, polymers, copolymers, terpolymers, and the like. Eachmaterial has its characteristic advantages and disadvantages forparticular applications including, for example, strength, amount ofstretch, and cost. The materials may be used singly or in combination,as appropriate.

In one configuration, the inside diameter of the unstretched tube 14 isat least as large as the compressed diameter of the line 12. When thetube 14 is in its unstretched state, that is, there is no tension forceon the tube 14, the line 12 can fully compress within the tube 14without causing radially stretching of the tube 14. In anotherconfiguration, the inside diameter of the unstretched tube 14 is atleast as large as the uncompressed diameter of the line 12. When thetube 14 is in its unstretched state, the fully compressed line 12 causesthe tube 14 to stretch radially.

There are a number of different ways known in the art to secure the tube12 to the braided line 14, both permanent and temporary. Depending onits form, the securement may be at the end 20 of the tube 14 or adjacentto the tube end 20. References in the present specification to thesecurement 16 being at the tube end 20 include all locations at oradjacent to the tube end 20 appropriate for the particular securement16.

The securement 16 must be strong enough to prevent separation of thetube 12 from the line 14 while at full extension. The present inventioncontemplates the use of three basic types of securements 16: adhesives,clamps, and shrink tubing.

Adhesives provide a chemical bond between the line 12 and tube 14. Theadhesive 30, which starts in liquid form, is placed between the line 12and tube 14 at the ends 20 of the tube 14, as FIG. 5, and allowed toharden. There are many different adhesives known in the art, and theselection of an appropriate adhesive is determined by the use to whichthe tie down 10 will be put. If, for example, the tube 14 is rubber andthe line 12 is nylon, only certain adhesives will bond to these twomaterials. Further, if the tie-down is for use in a wet or high-moistureenvironment, the number of adhesives is further limited. Adhesivematerials include silicones, cyanoacrylates, epoxies, polyurethanes,polymers, polysilicones, and elastomers.

Clamps are mechanical securements. There are permanent clamps, such ascrimps, and there are temporary clamps, such as hose clamps. A crimpsecurement is shown in FIG. 6. A non-continuous metal ring 34 is placedaround the tube 14 within which is the line 12. The abutting ends 36 ofthe ring 34 are pressed inwardly against the tube 14, which pressesagainst the line 12. The pressure from the ring ends 36 secures the line12 and tube 14 together. Crimps are not a preferred method of securementbecause they weaken the tube 14 and line 12 by cutting into the tube 14,shorting the useful life of the tie down 10. Hose clamps that use ascrew mechanism for tightening can provide a temporary securement, butcan also weaken the tube 14.

Shrink tubing is a hollow tube that shrinks in diameter upon theapplication of heat. The amount of shrinkage is a function of thematerial from which the tubing is made. It provides a secure attachmentby shrinking enough to form a strong friction fit between itself and theitem within. For the present invention, the shrink tubing 32 is positionover the end 20 of the tube 14 extending to either side, as in FIG. 5.Heat is applied to the shrink tubing 32 until it is in the desiredstate. Since the tube 14 is elastic, the shrink tubing will press in onthe tube 14, pressing it against the line 12. Shrink tubing is availablein a number of different materials, including neoprene, polyvinylchloride, polyolefin, KYNAR polymer, MYLAR polyester, and TEFLON.

As the tie down 10 is stretched and relaxed, the line 12 rubs on theinner surface of the tube 14. The rubbing can cause the line 12 and/ortube 14 to abrade and weaken. Optionally, in order to reduce the amountof abrasion, a lubricant 26 may be placed in the tube 14, as shown inFIG. 5. Liquid lubricants are not particularly desirable because theycan leak from the ends of the tie down 10 and, being oil based, maycause degradation of the line 12 and/or tube. Solid lubricants 26, inthe form of a dry powder, are more desirable. Graphite and molybdenumdisulfide (MoS₂) are the predominant materials. Other materials includeboron nitride, polytetrafluorethylene (PTFE), talc, calcium fluoride,cerium fluoride, and tungsten disulfide.

There are two basic methods for constructing the tie down 10. In thefirst, the line 12 is threaded through the tube 14 and one end issecured. Then the line is compressed into the tube 14 and the second endis secured. This method works when the inside diameter of the tube 14 isat least the compressed diameter of the line 12. In the second method,the line 12 is threaded through the tube 14 and one end is secured. Thenthe tube 14 is stretched to its full design length and the second end issecured. This method works for either configuration of line and tubediameters.

The ends of the tie down 10 are configured for attachment, as at 18,with the configuration depending upon the use to which the tie down 10is being put. In FIG. 1, the line 12 extends beyond the ends 20 of thetube 14. The line ends 24 can be configured as desired. Examples includeforming into a loop 38 and/or attaching a hook 40, as in FIG. 1, leavingthe line free, or other attachments as desired.

Alternatively, the line 12 does not extend from the tube ends 20 andanother mechanism for attachment is used. In one example, shown in FIG.7, a hook 42 extends from a crimp 44 that secures the line 12 to thetube 14.

It is also contemplated by the present invention that each end can beconfigured for attachment differently.

Thus it has been shown and described an elastic tie down which satisfiesthe objects set forth above.

Since certain changes may be made in the present disclosure withoutdeparting from the scope of the present invention, it is intended thatall matter described in the foregoing specification and shown in theaccompanying drawings be interpreted as illustrative and not in alimiting sense.

1. A tie down for connecting two objects, said tie down comprising: (a)an elastic tube having an unstretched state, a stretched state, and twoends; (b) a braided line extending through said tube, said line having acompressed state and an uncompressed state; and (c) a securement at eachof said tube ends to secure said line to said tube wherein said line isin said compressed state when said tube is in said unstretched state andsaid line is in said uncompressed state when said tube is in saidstretched state.
 2. The tie down of claim 1 further comprisingattachments for attaching to each of said objects.
 3. The tie down ofclaim 1 wherein said line extends from the ends of said tube.
 4. The tiedown of claim 1 wherein said tube has an inside diameter in saidunstretched state that is at least as large as a diameter of said linein said compressed state.
 5. The tie down of claim 1 wherein said tubehas a inside diameter in said unstretched state that is at least aslarge as a diameter of said line in said uncompressed state.
 6. The tiedown of claim 1 wherein said securement includes an adhesive.